6. Comments of Group Members 1. Materials Used 2. Design 3. Application of Physics Principles 4. Results of Experiment 5. Conclusion and Discussion

Polystyrene Plastic bag Plastic string LinenRubber band Cotton

Polystyrene Cotton Plastic string Plastic bag

The length of plastic strings affect the effective parachute surface area. It is the actual surface area of parachute that affect the air resistance. The longer the plastic strings, the smaller the angles the plastic strings made with the vertical. Then the horizontal component of tension of plastic strings Tsin θ becomes smaller. So the effective parachute surface area increases and air resistance increases too.

The surface area of parachute should be large to increase air resistance. Air resistance can balance the weight ( gravitational force). Then there is no net force acting on the parachute hence no acceleration. The final speed is called terminal speed. When the air resistance increases, the parachute reaches its terminal speed within a short time as the acceleration is decreasing. By F=(mv-mu)/t, when the final landing velocity decreases, the impact force decreases too.

The mass of parachute should be as small as possible. By F=(mv-mu)/t, when the mass decreases, the impact force decreases. The lower part of parachute should be wrapped with cotton and polystyrene. When the lower part of parachute hits the ground, the cotton and polystyrene contract because of pressure. Hence the impact time increases. By F=(mv-mu)/t, when the impact time increases, the impact force decreases.

1.The egg and the parachute landed safely from fourth floor in the New Wing of our school to the ground. The egg did not break. 2. The parachute reached its terminal speed within a very short time. 3. During the falling, the parachute fell down directly. It did not hit anything. 4. It took about 4.8s to reach the ground.

Surface area of plastic bag (increase air resistance) Cotton and polystyrene (shock absorber) Small mass of parachute (reduce impact force) Long plastic strings (increase the effective parachute surface area) Conclusion: All the following factors ensures the egg to be safe:

he surface area of plastic bag becomes larger to increase air resistance. 2.The appearance of the lower part of parachute can be modified. Discussion: The parachute could perform better if the following things are done:

At first, we thought a parachute for an egg can be easily made. But during the making process, we found that it was quite difficult to decide on the appearance and the materials to be used. Before we surfed on the Internet, we did not know that even the number of strings also affect the falling of the parachute. Although we spent lots of time to prepare this project, we were happy when we knew that the egg did not break after the experiment and all of us have learnt a lot from it.